This invention relates in general to subsea production systems, and in particular to an apparatus and method for connecting lines between subsea equipment using a subsea deployable drum.
Subsea installations often require the deployment of lines between one subsea piece of equipment and another. These lines, often called jumpers, may extend from a subsea well to a pipeline end termination and surface production flowline. Also, they may provide electrical power, electrical communications, optical communications, hydraulic power and chemicals to subsea trees, manifolds and distribution units. Typical lengths may vary from 20 meters to 4 kilometers, and cross-sections of lines or bundles of lines may be as much as 100 mm. in diameter. Typically, such lines are installed from a reel located on a pipeline laying vessel at the surface. Normally, such lines have a tensile armor exterior to protect them during installation.
A method of deploying a line subsea is provided in this invention that includes wrapping a length of line onto a rotatable drum of a deployment unit. The unit is lowered into the sea from a surface vessel. Then the drum is rotated to deploy the line. In the preferred method, the first end of the line is connected to a first subsea component, then the line is then removed entirely from the drum, and the second end of the line is connected to a second subsea component.
Preferably, the drum is powered and the unit is guided by an ROV (remote operated vehicle) that is lowered into the sea from the surface vessel on an umbilical line. The ROV stabs into an interface on the unit to provide the power to rotate the drum. The ROV also supplies thrust to move the unit horizontally while the line is being deployed. Further, the ROV disengages from the unit and connects the first and second ends to the subsea assemblies.
In one embodiment, the unit has a quick release upper section that releases from the lower section. The motor and controls interface are mounted to the upper section while the drum is mounted to the lower section. In the event of an emergency or malfunction, the ROV disconnects fasteners that fasten the upper and lower sections to each other. This allows the upper section and motor to be retrieved while the lower section and drum remain on the sea floor.